This invention relates to an assist device for the shift operation of marine propulsion system and more particularly to an improved transmission control.
A very popular type of transmission and one which finds wide utility in marine propulsion units employs a pair of counter-rotating bevel gears that are journalled on an output shaft. A dog clutching element is splined on this output shaft and is axially moveable along it into engagement with either one of the driven bevel gears so as to drive the output shaft selectively in forward or reverse direction. In conjunction with such shifting mechanisms, the load required to move the dog clutching element from its engaged position to its disengaged position is quite high. This is particularly true when it is attempted to make a shift with the driven gears being driven at a high rotational speed.
In connection with such transmissions it has, therefore, been proposed to employ a shift assist mechanism which temporarily reduces the engine speed during the time when the transmission is being moved from its driven position. In order to sense the shifting condition, a wide variety of controls have been provided. For the most part, these controls incorporate some form of spring bias lost motion connection so that when high shifting loads are encountered, lost motion is permitted. This lost motion movement is then utilized to actuate a switch for controlling the ignition circuit of the engine to provide speed reduction. Of course, such devices introduce lost motion in the shift mechanism which is not particularly desirable. Furthermore, the use of lost motion connections can require adjustment and limit significantly where the shift assisting device can be located in the system connecting the shift operator with the shifted element.
It is, therefore, a principal object of this invention to provide an improved shift assisting device for a transmission.
It is a further object of the invention to provide a shift assisting device which does not necessitate the incorporation of lost motion in the connection between the shift operator and the shift element.
It is a further object of this invention to provide an improved assisting device wherein the shift sensor can be positioned anywhere in the linkage system between the shift operator and the shift element.